You can keep anemones of the same species in the same tank without issue. Even touching. You may not want to listen to your LFS about anemones. There are reports of E. quadracolor/BTA from different clones not getting along, but I have no personal experience with this. Most seasoned anemone keepers believe that different species can cause problems for each other, even if they don't come into direct contact. I have mixed different species many times, and I've seen negative symptoms that I believe were caused by other species in the tank. I just gave away a very healthy malu because I believe it was using chemical warfare against my haddoni. Within two days of removing the malu, my haddoni doubled its expansion.